The focus of this proposal is to define chemopreventive mechanisms and molecular targets responsible for NSAID induced, COX-independent, apoptosis and growth inhibition of premalignant and malignant human oral cells. The hypothesis to be tested is that the chemopreventive effects of NSAIDs in human premalignant and malignant oral cell phenotypes are associated with mitochondrial triggering of molecular events leading to apoptosis. Mitochondria play a pivotal role in the processing of apoptotic signals, and in the storage and release of apoptogenic proteins leading to cell death. Our preliminary data indicate that celecoxib induces apoptosis and growth inhibition, independent of COX-2 inhibition, by acting on multiple components of signaling pathways regulating the stability of the mitochondrial membrane potential and follows prolonged cell cycle arrest. The loss of mitochondrial membrane potential leads to the activation of caspases 9, 3 and 8. The hypothesis will be tested using celecoxib and non-COX inhibiting structural analogs (celecoxib/derivatives) in a human oral cell culture model (normal, premalignant and malignant oral cell lines) and a xenografted oral cancer cell SCID mouse model. Pharmacological and genomic approaches will be used to define the molecular targets in signaling pathways leading to agent induced mitochondrial membrane instability, apoptosis and growth inhibition. Specific aim 1 will address hypotheses, and define mechanisms, by which celecoxib/derivative induce apoptosis in premalignant and malignant human oral cells. Specific aim 2 is designed to understand the relationship of celecoxib/derivative induced cell cycle arrest and apoptosis. Specific aim 3 will test the hypothesis that the in vitro molecular mechanisms for growth inhibition and apoptosis prevent tumor spread and recurrence in vivo. In specific aim 4 we will identify, in vivo, molecular targets responsible for growth inhibition of xenotransplanted tumors. The significance of this project will be to advance our understanding of the role of mitochondria in chemopreventive agent induced apoptosis, identify and characterizing novel molecular targets responsible for NSAID induced apoptosis and lay the foundation for the development of new chemopreventive agents in human oral cancer.